Two-beam laser annealing with improved temperature performance

Abstract

Systems and methods are disclosed for performing laser annealing in a manner that reduces or minimizes wafer surface temperature variations during the laser annealing process. The systems and methods include annealing the wafer surface with first and second laser beams that represent preheat and anneal laser beams having respective first and second intensities. The preheat laser beam brings the wafer surface temperate close to the annealing temperature and the anneal laser beam brings the wafer surface temperature up to the annealing temperature. The anneal laser beam can have a different wavelength, or the same wavelength but different orientation relative to the wafer surface. Reflectivity maps of the wafer surface at the preheat and anneal wavelengths are measured and used to select the first and second intensities that ensure good anneal temperature uniformity as a function of wafer position. The first and second intensities can also be selected to minimize edge damage or slip generation.

What is claimed is: 
     
       1. A method of non-melt annealing a semiconductor substrate having a patterned surface and a melt temperature, comprising:
 scanning at least one first laser beam over the patterned surface, the at least one first laser beam being configured in a first incidence plane and having a first wavelength and a first intensity that heats the patterned surface to a preheat temperature that is below the melt temperature and less than an anneal temperature; and 
 scanning at least one second laser beam over the patterned surface and relative to the first laser beam, the at least one second laser beam being configured in a second incidence plane and having a second wavelength and a second intensity that heats the patterned surface from the preheat temperature up to the anneal temperature; and 
 selecting the first and second intensities to achieve the anneal temperature while minimizing at least one of edge damage and slip generation. 
 
     
     
       2. The method of non-melt annealing according to  claim 1 , wherein the first wavelength is infrared and the second wavelength is different from the first wavelength. 
     
     
       3. The method of non-melt annealing according to  claim 1 , further comprising:
 the first laser beam defining a preheat line image at the patterned surface; 
 the second laser beam defining an anneal line image at the patterned surface; and 
 wherein the anneal line image falls entirely within the preheat line image. 
 
     
     
       4. The method of non-melt annealing according to  claim 3 , further comprising providing one of the preheat line image and the at least one anneal line image to have a length that corresponds to a size of a region of the patterned surface. 
     
     
       5. The method of non-melt annealing according to  claim 1 , further comprising varying at least one of the first and second intensities of the first and second laser beams during the scanning of the first and second laser beams. 
     
     
       6. The method of non-melt annealing according to  claim 1 , wherein the second laser beam increases the patterned surface temperature to the anneal temperature, wherein the amount of patterned surface temperature increase is in the range of between 200° C. and 800° C. 
     
     
       7. The method of non-melt annealing according to  claim 6 , wherein the anneal temperature is about 1,300° C. 
     
     
       8. The method of non-melt annealing according to  claim 1 , wherein the first laser beam raises the patterned surface temperature to be in the range from about 500° C. to about 1,100° C. 
     
     
       9. A system for laser annealing a semiconductor wafer having a patterned surface with first and second reflectivity maps at respective first and second wavelengths and an anneal temperature that is below a melt temperature of the wafer, comprising:
 a first laser system configured to generate a first laser beam having the first wavelength and a first intensity and scan the first laser beam over the patterned surface in a first incident plane to heat the patterned surface to a preheat temperature; 
 a second laser system configured to generate a second laser beam having the second wavelength and a second intensity and scan the second laser beam over the patterned surface in a second incident plane relative to the first incident plane of the first laser beam, the second laser beam being configured to heat the patterned surface from the preheat temperature to the anneal temperature; and 
 wherein the first and second intensities are selected based on the first and second reflectivity maps to reduce an amount of surface temperature variation during the scanning of the first and second laser beams as compared to annealing the patterned surface of the semiconductor wafer with only the second laser beam. 
 
     
     
       10. The system for laser annealing a semiconductor wafer according to  claim 9 , further comprising:
 the first laser beam defining a preheat line image at the patterned surface; 
 the second laser beam defining an anneal line image at the patterned surface; and 
 the first and second laser systems being configured so that the anneal line image resides entirely within the preheat line image. 
 
     
     
       11. The system for laser annealing a semiconductor wafer according to  claim 9 , further comprising a controller operably arranged to vary at least one of the first and second intensities when the first and second laser beams are scanned. 
     
     
       12. The system for laser annealing a semiconductor wafer according to  claim 9 , wherein the first wavelength is an infrared wavelength and the second wavelength is different from the first wavelength. 
     
     
       13. The system for laser annealing a semiconductor wafer according to  claim 9 , further comprising the second intensity being sufficient to increase the patterned surface temperature up to the anneal temperature, wherein the amount of patterned surface temperature increase is in the range of between 200° C. and 800° C. 
     
     
       14. The system for laser annealing a semiconductor wafer according to  claim 13 , wherein the second laser beam defines the anneal temperature to be about 1,300° C. 
     
     
       15. The system for laser annealing a semiconductor wafer according to  claim 9 , wherein the first laser beam defines the pre-heat temperature to be in the range from about 500° C. to about 1,100° C. 
     
     
       16. The system for laser annealing a semiconductor wafer according to  claim 9 , further comprising:
 the first laser beam defining a preheat line image at the patterned surface, the pre-heat line image has a length L 1  in the range 5 mm≦L 1 ≦20 mm. 
 
     
     
       17. The system for laser annealing a semiconductor wafer according to  claim 16 , further comprising:
 the second laser beam defining an anneal line image at the patterned surface, the anneal line imaging having a length L 2  that is substantially the same as length L 1  of the pre-heat line image.